Art of combustion of liquid fuels



May 7, 1935.- E. H.' cARRu'rHERs y 2,000,530

` I ART OF COMBUSTION OF LIQUID FUELS Fi1ed lay 19, 1931 3 sheets-sheet1 iINVENToR. BY l/ ATTORNEY.

May 7, 1935-v E. H. cARRuTHl-:Rs 2,000,580

ART OF COMBUSTION 0F LIQUID FUELS Filed May 19, 1931 '5 Sheets-Sheet 2Cowrv/vr Volcans PUMP A TTORNE Y.

May 7, 1935. E. H, cz/luaRLrHERsn 2,000,580

.ART 0F COMBUSTION OF LIQUID FUELS Filegi hay 19. 1931 s sheets-sheet 3Figa co was ,al ffl/Y I' BY ATTORNEY.

Patented May 7, 1935 2,000,580 A Aar or commsfnon oF maum Fons Y Eben H.Carruthers, Ithaca, N. Y., assignor to United Furnace EngineeringCompany, Inc., New York, N. Y., a corporation of Delaware ApplicationMay 19, 1931, Serial No. 538,453

This invention relates to the art of combustion of liquid fuels,particularly oil, especially for use in the burners of furnaces inwhichlclose control'of the` combustion and resulting 8856s is 5desirable.

In all prior liquid fuel combustion systems of i which I am aware, theregulation of the flow of liquid fuel is by the employment ofa valvewhich is designed to control the pressure back of the 0 burner orifice,or by an automatic pressure re- -ducing valve to maintain a constantpressure \back of the orifice, or combinations of both. Under the oldsystems, it has been practically impossibleto maintain the flow rate ofthe oil constant with xed settings of the pressure ulators and valves. A

For example, changes in temperature of the-oil, in the viscosity of theoil, or the building up of reg- ` .said material in the valve ororifice, may cause wide variations in flow. These variations must -becounteracted by constant manipulation of the valve or regulator, ifconditions are to be kept at all constant. \The' result of theuctuations is a flame of uneven character, and thegases of combustionmay become very detrimental to the articles in the furnace to which theheat -is applied.

v In.me1ting metals metals, it is very desirable to maintain a Ycertainselected' furnace atmosphere or composition of gases of combustion, toavoid certain detrimental eects on the materials subjected to heat. Forexample, in melting copper, a highly oxidizing atmosphere will causeoxidization of the copper; on the other hand, a highly reducing flamewill allow the copper to absorb carbon monoxide, which is known to bedetrimental to the metal. In-the case of heat treatment or annealing offerrous metal, an oxidizing ame is injurious to the surface of themetal, causing scaling; and therefore control of this atmosphere isdesirable again.

A neutral atmosphere which is the dividing line or small range betweenthe oxidizing and the reducing atmosphereis usually the most desirableto maintain, but in apparatus` novvI in use the setting of the valves orother parts is done by purely human observation of the operator, whichcannot be relied on at all times.

I Since it is desirable to maintain some particular atmosphere. it isnecessary to have a constant liiow rate 4of liquid fuel to the burnenginorder to avoid theuctuations in thepratio of the fuel to air mixture,which in turn causes fluctuations in the resulting furnace atmosphere,and

or in heat treatmentA of passage of the liquid fuel from the pump tolthelv burner.'

be high,` running, for example,"from 1000 pounds it is necessary tomaintain a constant liquid fuel ilcw rate along with the flow rate ofair that is I se An object of the present invention is to .provide a newand improved method of and apparatus for producing a constant selectedor predetermined furnace atmosphere or composition of gases of lcombustion within a furnace.

Other objects are, to provide means for effecting a Iconstant flow rateof liquid fuel and vmixing said fuel with the desired proportions of yairto maintain combustion, said liquid fuel being preferably atomizedprior to its mixture with the air, whereby air may be supplied at lowpressures; to provide a. system of burning liquid fuel which allows theselection of a certain furnace atmosphere, and which includes means for`indicating the said `furnace atmosphere .and means fou` maintaining theselected atmosphere without variations; and' a method and appara- 20 tusfor high combustion eiiiciency, applicable for utilizing fuel oils ofhigh, low and intermediate gravities. l

Inv the accompanying drawings, which illustrate various types ofapparatus embodying my invention and capable .of use in the practice ofmy method:

Figs. 1, 2 and 3 are diagrammatic views of several forms of apparatusembodying my invention. I 30 Referring first to the form of Fig. 1, 5designates preferably a volumetric flow displacement pump designed to bedriven by va suitable prime mover or motor 6 at a constant speed. Thispump is coupled to a liquid fuel storage tank 'I by a suitable pipeconnection 8, and is designed to deliver the .liquid fuel, preferablyoil,v to a burner designated generally. by the numeral 9. I8 designatesa connecting pipe line for the The burner \9 has a discharge orifice II; the area of this orifice should be of a size so that, for a setdeliveryrate, the pressure behind it will to 10,000 pounds per` squareinch.

' The pressures now known :to the art for spraying liquid fuels cannotbe accurately called high pressures since they are but a small fractionof the high pressures employed present invention.' At the novelpressures of 1000 to 10,000 pounds per square inch, the strain energysupplied in such. quantities that when the pressure is released, thisenergy is absorbed as surface tension in the particles which at theaccording to the 50 pressures mentiond are necessarily of suchproportions as to present the requisite surface for the absorption,which' energy is sumcient to cause vaporization or volatilization of theoil when the pressure is released, it thus being impossible for the oil4particles to remain as -drop- A lets and condense or coalesce ofthemselves as in existing methods since the entire quantity of liberatedoil heretofore was not completely blown into -a gas but the divisionHofthe oil under the action of pressure was 4flnal at a stage where themaior portion of the oil consisted of droplets of considerable size;hence by means of my invention, in combination with a ame, uponliberation of the oil, I efiect complete atomizatiomg,

vaporization and combustion directly at the orifice. This action occursimmediately, simultaneously land instantaneously, all of the oil beingblown directly and completely into a vaporous or volatile state solelythrough pressure. Accordingly the specific pressures are not limitar-ybut include all equivalent lowerand higher pressures which produce thesame results within the spirit and scope of the invention.

It is an important and characteristic feature of my invention that theliquid fuel is passed to the burner at a constant flow rate, and this Iaccomplish without the employment of valves or regulating meansinterposed vbetween the pump and the burner, as has heretofore beennecessary.

In practice, the pump should displace, in a unit of time, a definiteamount of liquid fuel regardless f the pressure it must discharge thisfuel against. so that the volume of liquid delivered to the burnerlthrough the connecting line I will be at a constant rate, regardless ofthe pressure in said line or back of the discharge orifice Il. c

Due to the presence of relatively high pressure backfof the dischargeoritlce, it will be apparent that the liquid fuel passing from the pumpto the burner will be broken up into fine particles and, as it i8discharged through the orifice, the drop in pressure from y the highvalues to the low pressure values will cause intense .atomization of theliquid fuel, rendering it suitable for complete combustion when mixedwith air. c

As illustrated in each of 'the forms of apparatus shown, air isdelivered to a furnace mixing chamber l2 of a furnace I3 from a fan orblower 20, and from thence the mixture of air and atomized liquid ispassed `to thecombustion chamber I4. of the furnace through an openingi5. Since the liquid fuel has been highly atomized upon leaving theoriiice Il, the air is not.

relied on totake any part in breaking up the liquid fuel; it is neededonly to mix with the atomized liquidy to support combustion,Consequently, the air employed may be low pressure air supplied from lowpressure fans, etc., at a considerable saving over present methods. Theemployment of low pressure air also has the effect of decreasing noiseinthe operation of the burner.

The rate at which the air is supplied to the combustion chamber,whenapparatus of the form of Fig. 1 is employed, may be controlled by avvalve or damper4 I6. disposed in the air line I1 connecting the blower20 and the chamber lz. rnaddmon to uns vave ls, and at som convenientlocation in line I1, I providel a. Venturi meter I8, or a thin plateorifice or its equivalent, communicating with a manometer or othersuitable indicator device I9. The function of4 this indicator device isto show relatively the weight-time rate of air passing through the lineto vthe combustion space of the furnace, by indicating the pressuredrop' through the meter.

The indicator device may be calibrated in terms of percentage of gascomposition of thel furmoe gases, thereby having the advantage of givingthe operator a definite scale by which he can regulate the atmosphere tosuit the requirements of the material being heated.

The furnace atmosphere, or the composition and relative proportions orthe gases resulting from this combustion, depend upon the relativeproportions or rates at which the fuel and air are being delivered.Since the fuel rate is definitely fixed at a certain value, changes inthe resulting gases will be effected by changes in the air rate only,which changes will be lindicated on the air flow indicator I9. For,every position of this indicator, then, there will be a correspondinganalysis of the gases resulting from combustion. These may be determinedby taking samples directly from the furnace and analyzing them by any ofthe generally known methods, and the resulting figures placed on theindicator. c

After analyses are made for a sufilcient number of. points to form thescales of the indicator, the sampling and analysis apparatus may bediscarded. From then on, the readings of the scales will indicate thecomposition of the gases, and the operator, by adjustment of theairvalve or gate, may bring the indicator to any particular scale readingand thus establish the corresponding furnace atmosphere.

In the operation of the form of Fig. 2, it is contemplated that the airflow is kept constant by a suitable automatic air dow regulator 2| andthepump 5 for the liquid fuel, regulated so that the rate of flow offluid 'may be varied to any selected krate, but after the selection therate of flow of the liquid will be constant. In this manner, the ratioof fuel to air may be selected and controlled so as to give the desiredresulting furnace atmosphere as described in connection with the form ofFig. l. apparatus, I employ, in place of the venturi meter I8, theregulator 2| of well known construction.v 'Ihis regulator may be set .toallow .varied by the employment of a variable speed motor; and thepercentages' of gases calibrated in terms of said speed.

The operation of the form-of Fig. 2 is substantially the sameasdescribed for the form of In this form of- Fig. 1, with the exceptionthat the changes in the composition and relative` proportionsof theproducts of combustion is eifected by manipulation of the' mechanicalvolumetric adjusting means of the pump, or alternatively, by regulacaladjustment of the pumpis displacement, or to the indicator of the pumpsspeed of rotation in the case of the speed adjustment.

Fig. 3 illustrates apparatus comprising a -combination of the forms ofFigs. l and` 2. In this ease, the positive blower or'fan .20 and theconstant volume displacement pump 5 are driven by the same power means6, through connecting shafts or suitable gearing. 'I'he pump 5 isprovided, as in Fig. 2, with the adjustable velumetric control means l22and the'dial or indicator 23, indicating the percentages of the gases ofcombustion as a function of the flow rate of liquid fuel therethrough.While the power means E is rotating at any desired constant speed, theoperation and control will be identicalwiththat oftheformofFig.2,theratecf speed of the blower 2li.v

Since the rate at which the blower delivers air and the flow rate of thepump 5 are proporsupplv of air being constant, due to the`constanttional to the speed at which said units aredriven.

'highly desirable in providing an accurate heat control for the vfurnaceto which the system is applied, and permits the furnace to be banked ormaintained at a minimum temperature when not in actual use. i

In priorliquid fuel combustion systems, the supplies of liquid fuel andair 'must be entirely shut olf when the furnace is not in actual use.Due to this fact, the furnaces, ovens. etc. cool ofi between heats andresult in considerable waste of fuel in bringing the apparatus toworking temperature forA the next heat.

I claim: v

l. The herein described method of effecting combustion of a liquid fuelwhich consists in prducing a fiow'of the liquid at a constant ow ratewhile subjected to high pressure at or above substantially 1000 poundsper square inch, atomizing said liquid by said pressure prior to itsymixture with air, and then mixing air and they atomized liquid inpredetermined proportions and igniting'the mixture.

2. The method according to claim l in which the air mixed within theatomized liquid is ata ,pressure relatively low with respect to the saiduid in the furnace and ignitlng the mixture.

4. The herein described method of effecting combustion of liquid fuel ina furnace, which' consists in producing a flow of the liquid by pres-Sure above substantially 1000 pounds per square inch at a constant flowrate. atomizing said liquid prior to its admixture with air, and then 6mixing ai' ln controlled and measured quantities with the atomizedliquid and igniting the mixture.

5. The herein described method of effecting combustion of liquid fuel ina furnace which consists in producing a ow of the liquid "at a constantflow rate, atomizing said liquid by pressure above or at substantially1000 pounds per square inch prior to its admixture with air, then mixingair in controlled quantities with the atl5 omized liquid and ienitlngthe mixture.

y 6. The herein described method of effecting combustion of a liquidfuel which consists in producing a flow of the liquid while subjected tohigh pressure at or above substantially 1000 pounds per square inch,atomizing said liquid by said'pressure prior to its admixture with air,mixing air and the atomized liquid, and igniting the said mixture. Y

7. 'I'he herein described method of effecting 25 combustion of a liquidfuel which consists in producing a flow of the liquid while subjected tohigh pressure at or above substantially 1000 pounds per square inch,atomizing said liquid by said pressure prior to its admixture with air,mixing low pressure air and the atomized liquid, and igniting the saidmixture.

8. The herein described method of effecting combustion of a liquid fuelwhich consists in producing a flow of the liquid while subjected to highpressure at or vabove substantially 1000 pounds per square inch,atomizing said liquid by said pressure prior to its admixture with air,mixing low pressure air and the atomized liquid in predeterminedproportions, and igniting the 40 said mixture.

9. The herein described method of eiecting combustion of a liquid fuelin a furnace to produce a selected constant furnace atmosphere withinthe furnace, which consists in supplying d5 a mixture vof air and liquidfuel to the furnace in constant quantities, the liquid fuel beingatomized at a.pressure at or above substantially v1000 pounds per squareinch, varying the quani tity of one ofthe fluids of the mixturewhilemaintaining the other constant, and igniting the mixture.

l0. The herein described method pf effecting combustion of liquid fuelin a furnace, which consists in producing a flow of the liquid at aconstant flow rate while subjected to a pressure at or abovesubstantially one thousand pounds per square inch to atomize the liquid,then mixf ing air in controlled and measured-quantities with theatomizea nquiasnd in simultaneouslyeffecting -equal changes in bothair'.and liquid flow for the purpose of changing'the rate of heatliberation in the furnace without. changing the Y vatmosphericcondition, andthenv igniting the

